Search Results

Some of the frequencies of transmission gear whine noise reach up to several kHz. High-frequency gear whine noise is mostly transmitted by air (airborne); therefore, it is critical to reduce transmission radiation noise. This paper presents how to solve the problem of high-frequency noise in the range of 2.0 - 4.1kHz by experiment using Inverse Boundary Element Method (IBEM) and by computer simulation using Boundary Element Method (BEM).

The present paper focuses on methods for estimating equivalent source positions or “hot spots” on an object to be modelled acoustically. This procedure is the first step in the derivation of an acoustic equivalent source model to be used e.g. in connection with measured acoustic transfer paths. Methods based on Near-field Acoustic Holography as well as the Inverse Boundary Element Method are described and compared. The use of the different methods is illustrated by actual measurements and calculations on a real passenger car exhaust line system.

The paper deals with the construction of a powertrain acoustic radiation model to be used as a noise source in acoustic finite or boundary element models. This model results from near-field acoustic measurements of the running powertrain. Transfer functions between the measurement points and a meshed envelope of the powertrain (850 nodes) are calculated using a boundary element model of the powertrain in the test-bench. Wave-Envelope vectors are then used as a projection basis to solve the inverse problem providing flow velocities on the surface of the powertrain model. The quality of the model is assessed by comparing computed and measured sound pressures at specific location, away from the initial measurement points. The original free-field configuration, as well as a confined situation, simulating an under-hood around the powertrain, are examined.

This paper presents a method for modelling Pass-By Noise from a light weight truck by using Direct and Inverse Boundary Element Techniques. One of the issues in evaluating Pass-By Noise of a vehicle is to assess the internal noise sources. In the present study, it is assumed that the noise is mainly due to sound radiation from the truck engine. Therefore a proper source model of the engine is derived by using an Inverse Boundary Element scheme involving experimental data and a boundary element model of the engine defined as a set of prescribed acceleration surfaces. Once the engine noise model has been derived, the Pass-by Noise is computed by using the standard Variational Boundary Element Method as packaged in I-DEAS Vibro-Acoustics of SDRC which includes RAYON-3D solver of STRACO SA. Finally, computed acoustics pressures at standardized Pass-By Noise locations are compared to experimental results.